JP7348039B2 - semiconductor light emitting device - Google Patents

Description

The present invention relates to a semiconductor light emitting device.

The semiconductor light emitting device described in Patent Document 1 includes an active layer, a pair of cladding layers sandwiching the active layer, and a phase modulation layer provided between the active layer and one of the cladding layers. The phase modulation layer includes a base layer and modified refractive index regions having a refractive index different from that of the base layer and arranged periodically in a two-dimensional manner in the base layer. The light generated in the active layer forms a two-dimensional standing wave in the phase modulation layer, oscillates in the in-plane direction, becomes laser light, and is emitted in the stacking direction.

Patent Document 2 describes an edge-emitting optical semiconductor device in which a stacked body of a double heterostructure is electrically separated into a gain region and a loss region by an ion implantation region. This optical semiconductor device can function as a superluminescent diode that outputs temporally incoherent light.

Japanese Patent Application Publication No. 2018-198302 Japanese Patent Application Publication No. 2018-182306

An object of the present invention is to provide a semiconductor light emitting device that can output incoherent light in the stacking direction.

The semiconductor light emitting device of the present invention includes an active layer, a first cladding layer and a second cladding layer sandwiching the active layer, and a space between the active layer and the first cladding layer or between the active layer and the second cladding layer. a laminate having an optical diffraction layer provided thereon; a first electrode and a second electrode provided on a second cladding layer so as to be spaced apart from each other; and a first electrode and a second electrode opposite to each other with respect to the laminate. at least one counter electrode provided on the side, the light diffraction layer having a refractive index different from that of the base layer, and having a refractive index in the base layer perpendicular to the thickness direction of the base layer. a plurality of modified refractive index regions periodically arranged along a plane, and the second electrode is located on both sides of at least a portion of the first electrode in one direction perpendicular to the lamination direction of the laminate. The laminate is provided with a separation region that electrically isolates a first region under the first electrode and a second region under the second electrode, and a plurality of different The refractive index region is provided in a portion of the base layer that overlaps with the first region when viewed from the stacking direction.

In this semiconductor light emitting device, a first electrode and a second electrode are provided on the second cladding layer so as to be spaced apart from each other, and a first region under the first electrode and a second region under the second electrode are separated. electrically separated from each other by regions. The second electrodes are arranged on both sides of at least a portion of the first electrode in one direction perpendicular to the stacking direction of the laminate. As a result, a forward bias is applied between the first electrode and the counter electrode to make the first region function as a gain region, and a reverse bias is applied between the second electrode and the counter electrode to make the second region function as a loss region. By functioning as such, resonance of light generated in the first region can be suppressed by the second regions on both sides of the first region, and incoherent light can be generated. Further, an optical diffraction layer is provided between the active layer and the first cladding layer or the second cladding layer, and the optical diffraction layer has a modified refractive index in a portion overlapping with the first region when viewed from the stacking direction. An area is provided. Thereby, incoherent light generated in the active layer can be diffracted by the optical diffraction layer and output in the stacking direction. Therefore, this semiconductor light emitting device can output incoherent light in the stacking direction.

The isolation region may include an ion implantation region, an impurity diffusion region, a semiconductor region having a different conductivity type from the second cladding layer, or a semiconductor region having a different impurity concentration from the second cladding layer. In this case, reflection of light in the separation region can be suppressed, and resonance of light generated in the first region can be suppressed more effectively.

The light diffraction layer may be provided between the active layer and the second cladding layer, and the separation region may extend from the second cladding layer to the light diffraction layer. In this case, electrical isolation between the first region and the second region can be further ensured.

The semiconductor light emitting device of the present invention further includes a semiconductor substrate, and the laminate is disposed on the semiconductor substrate such that the first cladding layer is located on the semiconductor substrate side with respect to the second cladding layer, and the laminate is arranged on the semiconductor substrate such that the first cladding layer is located on the semiconductor substrate side with respect to the second cladding layer. The layer may be provided between the active layer and the second cladding layer. In this case, during manufacturing, the optical diffraction layer can be formed after forming the active layer on the semiconductor substrate. Therefore, compared to the case where the active layer is formed after forming the optical diffraction layer, the flatness of the active layer can be ensured more reliably.

The plurality of modified refractive index regions may be provided in the base layer over a portion overlapping with the first region and a portion overlapping with the second region when viewed from the stacking direction. In this case, the arrangement end of the modified refractive index region is located in the second region, and it is possible to reliably suppress light resonance caused by reflection at the arrangement end.

The first electrode may have a linearly extending portion. In this case, the width of the first region can be narrowed, and resonance of light generated in the first region can be suppressed more reliably.

The first electrode may have a plurality of first linear parts, and the second electrode may have a plurality of second linear parts arranged alternately with the plurality of first linear parts. In this case, the width of the first region can be narrowed, and resonance of light generated in the first region can be suppressed more reliably. Furthermore, a large light output area can be secured.

The first electrode may be surrounded by the second electrode when viewed from the stacking direction. In this case, the resonance of light generated in the first region can be effectively suppressed by the second region surrounding the first region.

When a group of virtual lattice points is set in the base layer along a plane perpendicular to the thickness direction of the base layer, the position of the center of gravity of each of the plurality of modified refractive index regions with respect to the lattice point is determined by a predetermined modulation. It may be set according to a pattern. In this case, light having a shape corresponding to the modulation pattern can be output in the stacking direction.

The first region functions as a gain region by being forward biased between the first electrode and the at least one counter electrode, and the second region functions as a gain region between the second electrode and the at least one counter electrode. By applying a reverse bias, it may function as a loss region. In this case, as described above, the resonance of light generated in the first region can be suppressed by the second regions on both sides of the first region, and incoherent light can be output in the stacking direction.

According to the present invention, it is possible to provide a semiconductor light emitting device that can output incoherent light in the stacking direction.

FIG. 1 is a plan view of a semiconductor light emitting device according to an embodiment. FIG. 2 is a bottom view of a semiconductor light emitting device. 2 is a sectional view taken along line III-III in FIG. 1. FIG. FIG. 3 is a diagram showing the arrangement of modified refractive index regions in a light diffraction layer. FIG. 7 is a plan view of a semiconductor light emitting device according to a first modification. FIG. 7 is a bottom view of a semiconductor light emitting device according to a first modification. 6 is a sectional view taken along the line VII-VII in FIG. 5. FIG. FIG. 7 is a plan view of a semiconductor light emitting device according to a second modification. FIG. 7 is a bottom view of a semiconductor light emitting device according to a second modification. 9 is a sectional view taken along line XX in FIG. 8. FIG. It is a figure which shows the arrangement|positioning of the modified refractive index area|region in a 3rd modification. It is a figure which shows the arrangement|positioning of the modified refractive index area|region in a 3rd modification. It is a figure which shows the arrangement|positioning of the modified refractive index area|region in a 4th modification. It is a figure which shows the arrangement|positioning of the modified refractive index area|region in a 4th modification. (a) to (c) are diagrams showing the arrangement of the first electrode and the second electrode in fifth to seventh modified examples. (a) and (b) are diagrams showing the arrangement of the first electrode and the second electrode in the eighth and ninth modified examples. (a) to (c) are diagrams showing the arrangement of the first electrode and the second electrode in the tenth to twelfth modifications. (a) and (b) are diagrams showing the arrangement of the first electrode and the second electrode in the thirteenth and fourteenth modified examples.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and overlapping description will be omitted.
[Structure of semiconductor light emitting device]

As shown in FIGS. 1 to 3, the semiconductor light emitting device 1A includes a semiconductor substrate 2 and a laminate 10. The laminate 10 includes a lower cladding layer 11 (first cladding layer), an active layer 12, an optical diffraction layer 13, an upper cladding layer 14 (second cladding layer), and a contact layer 15, which are formed on the surface 2a of the semiconductor substrate 2 in this order. It is constructed by stacking layers on top of each other. That is, the laminate 10 is arranged on the semiconductor substrate 2 such that the lower cladding layer 11 is located on the semiconductor substrate 2 side with respect to the upper cladding layer 14. Active layer 12 is sandwiched between lower cladding layer 11 and upper cladding layer 14 . The optical diffraction layer 13 is provided between the active layer 12 and the upper cladding layer 14. In the following description, the stacking direction of the laminate 10 will be referred to as the Z direction, one direction perpendicular to the Z direction will be referred to as the X direction, and the direction perpendicular to the Z direction and the X direction will be referred to as the Y direction. The thickness direction of the semiconductor substrate 2 and each of the layers 11 to 15 is parallel to the stacking direction of the stacked body 10.

The optical diffraction layer (diffraction grating layer) 13 includes a base layer 21 and a plurality of modified refractive index regions 22 provided in the base layer 21. The modified refractive index region 22 is a region having a refractive index different from that of the base layer 21. The modified refractive index regions 22 are arranged periodically in the base layer 21 along a plane (XY plane) perpendicular to the thickness direction of the base layer 21 . Details of the optical diffraction layer 13 will be described later.

The semiconductor substrate 2 and each of the layers 11 to 15 are made of a compound semiconductor such as a GaAs-based semiconductor, an InP-based semiconductor, or a nitride-based semiconductor. As an example, the semiconductor substrate 2 is a GaAs substrate. The lower cladding layer 11, the active layer 12, the optical diffraction layer 13, the upper cladding layer 14, and the contact layer 15 are composed of elements included in the group consisting of Group III elements Ga, Al, and In and Group V elements As. This is a compound semiconductor layer. As a specific example, the lower cladding layer 11 is an AlGaAs layer, the active layer 12 has a multiple quantum well structure (for example, the barrier layer is made of AlGaAs and the well layer is made of InGaAs), and the upper cladding layer 14 is made of AlGaAs. The contact layer 15 is a GaAs layer.

The lower cladding layer 11 is given the same conductivity type as the semiconductor substrate 2, and the upper cladding layer 14 and the contact layer 15 are given the opposite conductivity type to the semiconductor substrate 2. In one example, semiconductor substrate 2 and lower cladding layer 11 are n-type, and upper cladding layer 14 and contact layer 15 are p-type. The optical diffraction layer 13 has a conductivity type opposite to that of the semiconductor substrate 2. The impurity concentration is, for example, 1×10 ¹⁷ to 1×10 ²¹ /cm ³ . Although each part is schematically shown in FIG. 3, the semiconductor substrate 2 is actually extremely thick compared to the stacked body 10.

The semiconductor light emitting device 1A further includes a first electrode (gain electrode) 4, a second electrode (absorption electrode) 5, and a counter electrode 6. The first electrode 4 and the second electrode 5 are provided on the upper cladding layer 14 via the contact layer 15 so as to be spaced apart from each other. The first electrode 4 and the second electrode 5 are electrically connected to the upper cladding layer 14 via the contact layer 15. A protective layer 16 is provided on the contact layer 15 so as to surround the first electrode 4 and the second electrode 5. The counter electrode 6 is provided on the back surface 2b of the semiconductor substrate 2 and is electrically connected to the semiconductor substrate 2. That is, the counter electrode 6 is provided on the side opposite to the first electrode 4 and the second electrode 5 with respect to the stacked body 10. The counter electrode 6 has an opening 6a. For example, the counter electrode 6 has a rectangular outer shape, and the opening 6a is formed in a rectangular shape (FIG. 2). An antireflection layer 17 is provided on the back surface 2b of the semiconductor substrate 2 so as to surround the counter electrode 6.

The first electrode 4, the second electrode 5, and the counter electrode 6 are made of, for example, an Au-based metal. The protective layer 16 is made of, for example, an insulating film of silicon nitride (eg, SiN), silicon oxide (eg, SiO ₂ ), or the like. The antireflection layer 17 is made of, for example, a dielectric single layer film or a dielectric multilayer film of silicon nitride (eg, SiN), silicon oxide (eg, SiO ₂ ), or the like. The dielectric multilayer film includes, for example, titanium oxide (TiO ₂ ), silicon dioxide (SiO ₂ ), silicon monoxide (SiO), niobium oxide (Nb ₂ O ₅ ), tantalum pentoxide (Ta ₂ O ₅ ), and fluoride. Dielectric layers such as magnesium oxide (MgF ₂ ), titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), cerium oxide (CeO ₂ ), indium oxide (In ₂ O ₃ ), zirconium oxide (ZrO ₂ ), etc. A film in which two or more types of dielectric layers selected from the group are laminated can be used. For example, films having a thickness of λ/4, which is an optical film thickness for light having a wavelength λ, are stacked.

As shown in FIG. 1, the first electrode 4 includes a plurality of (six in this example) first linear portions 4a and a first connection portion that connects the ends of the first linear portions 4a. 4b. Each first linear portion 4a is formed in a rectangular layer shape and extends linearly along the X direction. The plurality of first linear portions 4a have the same shape and are lined up along the Y direction. The first connecting portion 4b is formed in a rectangular layered shape and extends linearly along the Y direction. That is, the first connecting portion 4b extends perpendicularly to the plurality of first linear portions 4a.

The second electrode 5 has a plurality of (six in this example) second linear parts 5a and a second connecting part 5b that connects the ends of the second linear parts 5a. . Each second linear portion 5a is formed in a rectangular layer shape and extends linearly along the X direction. The plurality of second linear portions 5a have the same shape and are lined up along the Y direction.

The plurality of second linear portions 5a are arranged alternately with the plurality of first linear portions 4a. That is, except for the second linear portion 5a located on the most one side (the uppermost side in FIG. 1) in the Y direction, each second linear portion 5a is located between two adjacent first linear portions 4a. It is located in In other words, the two adjacent second linear portions 5a are located on both sides of the first linear portion 4a in the Y direction (arranged to sandwich the first linear portion 4a in the Y direction). ).

The second linear portion 5a extends parallel to the first linear portion 4a. The plurality of first linear portions 4a and the plurality of second linear portions 5a are arranged at equal intervals along the Y direction. The second linear portion 5a has the same shape as the first linear portion 4a. The second connection portion 5b is formed in a rectangular layered shape and extends linearly along the Y direction. That is, the second connecting portion 5b extends perpendicularly to the plurality of second linear portions 5a. The second connecting portion 5b extends parallel to the first connecting portion 4b. The second connecting portion 5b has the same shape as the first connecting portion 4b.

A separation region (current shielding region) 18 is provided in the stacked body 10 . The separation region 18 electrically separates the first region 101 under the first electrode 4 from the second region 102 under the second electrode 5 in the stacked body 10 . The first region 101 is a region immediately below the first electrode 4, and is a region that overlaps with the first electrode 4 in the stacked body 10 when viewed from the Z direction. The second region 102 is a region immediately below the second electrode 5, and is a region that overlaps with the second electrode 5 in the stacked body 10 when viewed from the Z direction.

The separation region 18 includes a plurality of first portions 18a extending between the first linear portion 4a and the second linear portion 5a when viewed from the Z direction, and a first straight portion when viewed from the Z direction. A plurality of first portions extend between the shaped portion 4a and the second connecting portion 5b or between the first connecting portion 4b and the second straight portion 5a, and connect the ends of the plurality of first portions 18a. It has two parts. Each first portion 18a extends along an XZ plane perpendicular to the Y direction. Each second portion extends along the YZ plane perpendicular to the X direction. Isolation region 18 extends from surface 15a of contact layer 15 to upper cladding layer 14 in the Z direction. The end of the separation region 18 extends beyond the midpoint of the upper cladding layer 14 in the Z direction and reaches the vicinity of the optical diffraction layer 13 .

The isolation region 18 is, for example, an ion implantation region formed by adding protons, boron, etc. to the stacked body 10 by ion implantation. Since the separation region 18 is composed of an ion-implanted region, the difference in refractive index between the separation region 18 and the first region 101 and the second region 102 can be reduced, and light reflection in the separation region 18 can be reduced. can be suppressed.

Details of the optical diffraction layer 13 will be explained with reference to FIG. 4. As described above, the optical diffraction layer 13 includes the base layer 21 and a plurality of modified refractive index regions 22 having a refractive index different from the refractive index of the base layer 21. When a group of virtual lattice points O is set on the optical diffraction layer 13 along the XY plane, the center of gravity G of each modified refractive index region 22 is located on the lattice point O. In this example, each lattice point O constitutes a square lattice. One side of the square lattice is parallel to the X direction, and the other side is parallel to the Y direction. The shape of each modified refractive index region 22 when viewed from the Z direction is, for example, circular. Each modified refractive index region 22 extends, for example, along the Z direction from the surface 21a of the base layer 21 on the upper cladding layer 14 side (FIG. 3). When the wavelength of light generated in the active layer 12 when driving the semiconductor light emitting device 1A is λ, and n is a natural number, the centers of gravity G of the modified refractive index regions 22 adjacent in the X direction or the Y direction are separated by nλ. There is.

As shown in FIG. 3, the plurality of modified refractive index regions 22 are located in a portion of the base layer 21 that overlaps with the first region 101 (the first electrode 4) and a second region 102 (the second region) when viewed from the Z direction. It is provided over the portion that overlaps with the electrode 5). In this example, the plurality of modified refractive index regions 22 are provided over the entire portion overlapping with the first region 101. Further, the plurality of modified refractive index regions 22 are also provided in a portion overlapping with the second region 102 so as to connect the portions overlapping with the first region 101. That is, the plurality of modified refractive index regions 22 are also provided in a portion overlapping with a second region 102 sandwiched between adjacent first regions 101 . Although the modified refractive index regions 23 are schematically shown in FIGS. 3 and 4, in reality, a large number of modified refractive index regions 22 are arranged at intervals shorter than those shown.

As an example, the base layer 21 is made of GaAs, and the modified refractive index region 22 is a hole. The modified refractive index region 22 may be formed by embedding a semiconductor having a different refractive index from that of the base layer 21 in the pores. In this case, the holes in the base layer 21 may be formed by etching. A semiconductor may be embedded into the holes using a metal organic vapor phase epitaxy method, a sputtering method, or an epitaxial method. After the modified refractive index region 22 is formed by burying a semiconductor in the pores of the base layer 21, the same semiconductor as the modified refractive index region 22 may be further deposited thereon. When the modified refractive index region 22 is a hole, the hole may be filled with an inert gas such as argon, nitrogen, or hydrogen, or air.
[Method for driving semiconductor light emitting device]

An example of a method for driving the semiconductor light emitting device 1A will be described. A forward bias is applied between the first electrode 4 and the counter electrode 6. For example, a positive voltage (for example, +1.5 to +2 V) is applied to the first electrode 4 with the counter electrode 6 at ground potential. Thereby, the first region 101 functions as a gain region, and the gain region attempts to oscillate light as a laser diode. On the other hand, a reverse bias is applied between the second electrode 5 and the counter electrode 6. For example, a negative voltage (for example, -5V) is applied to the second electrode 5 with the counter electrode 6 at ground potential. Thereby, the second region 102 functions as a loss region (absorption region), and the loss region attempts to stop optical oscillation as a laser diode. As a result, the first region 101 and the second region 102 function as superluminescent diodes, and temporally incoherent light is generated. In FIG. 3, a region of the active layer 12 that functions as a gain region during driving is indicated by reference numeral 12a, and a region that functions as a loss region is indicated by reference numeral 12b.

The light generated in the active layer 12 is diffracted by the optical diffraction layer 13 and forms a two-dimensional standing wave according to the lattice structure of the optical diffraction layer 13 (the arrangement pattern of the modified refractive index regions 22). The planar light thus formed passes through the active layer 12, the lower cladding layer 11, and the semiconductor substrate 2, and is output from the back surface 2b of the semiconductor substrate 2 along the Z direction. In this example, the output light is output from the opening 6a of the counter electrode 6, as indicated by the arrow in FIG.
[Action and effect]

In the semiconductor light emitting device 1A, the first electrode 4 and the second electrode 5 are provided on the upper cladding layer 14 so as to be spaced apart from each other. The two regions 102 are electrically isolated from each other by the isolation region 18. The second electrode 5 is arranged to be located on both sides of at least a portion of the first electrode 4 in the Y direction. As a result, a forward bias is applied between the first electrode 4 and the counter electrode 6 to cause the first region 101 to function as a gain region, and a reverse bias is applied between the second electrode 5 and the counter electrode 6 to cause the first region 101 to function as a gain region. By making the second region 102 function as a loss region, the resonance of light generated in the first region 101 can be suppressed by the second regions 102 on both sides of the first region 101, and incoherent light can be prevented from being generated. can. Further, an optical diffraction layer 13 is provided between the active layer 12 and the upper cladding layer 14, and the optical diffraction layer 13 has a modified refractive index region in a portion overlapping with the first region 101 when viewed from the Z direction. 22 are provided. Thereby, incoherent light generated in the active layer 12 can be diffracted by the optical diffraction layer 13 and output in the Z direction. Therefore, the semiconductor light emitting device 1A can output incoherent light in the stacking direction (Z direction).

Isolation region 18 is constituted by an ion implantation region. Thereby, reflection of light in the separation region 18 can be suppressed, and resonance of light generated in the first region 101 can be suppressed more effectively.

The stacked body 10 is arranged on the semiconductor substrate 2 such that the lower cladding layer 11 is located on the semiconductor substrate 2 side with respect to the upper cladding layer 14, and the optical diffraction layer 13 is located between the active layer 12 and the upper cladding layer 14. It is provided between the layer 14 and the layer 14. Thereby, the optical diffraction layer 13 can be formed after the active layer 12 is formed on the semiconductor substrate 2 during manufacturing. Therefore, the flatness of the active layer 12 can be ensured more reliably than in the case where the active layer 12 is formed after the optical diffraction layer 13 is formed.

A plurality of modified refractive index regions 22 are provided in the base layer 21 over a portion overlapping with the first region 101 and a portion overlapping with the second region 102 when viewed from the Z direction. Thereby, the arrangement end of the modified refractive index region 22 is located in the second region 102, and it is possible to reliably suppress light resonance caused by reflection at the arrangement end.

The first electrode 4 has a first linear portion 4a that extends linearly. Thereby, the width of the first region 101 can be narrowed, and the resonance of light generated in the first region 101 can be suppressed more reliably.

The first electrode 4 has a plurality of first linear parts 4a, and the second electrode 5 has a plurality of second linear parts 5a arranged alternately with the plurality of first linear parts 4a. There is. Thereby, the width of the first region 101 can be narrowed, and the resonance of light generated in the first region 101 can be suppressed more reliably. Furthermore, a large light output area can be secured.
[Modified example]

In the semiconductor light emitting device 1B of the first modification shown in FIGS. 5 to 7, the first electrode 4 is formed in a circular shape and the second electrode 5 is formed in a circular shape when viewed from the Z direction. . The first electrode 4 is surrounded by the second electrode 5. In other words, the second electrode 5 is located on both sides of the first electrode 4 in any direction perpendicular to the Z direction. That is, the second electrode 5 is located on both sides of the first electrode 4 in each of the first direction perpendicular to the Z direction and the second direction perpendicular to both the Z direction and the first direction. . The separation region 18 extends in an annular shape between the first electrode 4 and the second electrode 5 when viewed from the Z direction.

Similarly to the semiconductor light emitting device 1A of the embodiment described above, the semiconductor light emitting device 1B of the first modification can also output incoherent light in the stacking direction. Further, the first electrode 4 is surrounded by the second electrode 5 when viewed from the Z direction. Thereby, the resonance of light generated in the first region 101 can be effectively suppressed by the second region 102 surrounding the first region 101.

In the semiconductor light emitting device 1C of the second modification shown in FIGS. 8 to 10, the first electrode 4 is formed in a circular shape when viewed from the Z direction, similarly to the semiconductor light emitting device 1A of the first modification. , the second electrode 5 is formed in an annular shape. The first electrode 4 is surrounded by the second electrode 5. In the semiconductor light emitting device 1C, the counter electrode 6 is provided on the entire back surface 2b of the semiconductor substrate 2. The counter electrode 6 is made of a material that is transparent to the wavelength of the output light, and is a transparent electrode. Antireflection layer 17 is provided on counter electrode 6 .

The optical diffraction layer 13 is provided between the active layer 12 and the lower cladding layer 11. The semiconductor light emitting device 1C is formed in a mesa shape. That is, the semiconductor substrate 2 has a first portion 2c and a second portion 2d wider than the first portion 2c. The laminate 10 is arranged on the surface 2a of the first portion 2c. The counter electrode 6 is provided on the back surface 2b of the second portion 2d. The output light passes through the counter electrode 6 and is output from the back surface 2b side of the semiconductor substrate 2. Similarly to the semiconductor light emitting device 1A of the embodiment described above, the semiconductor light emitting device 1C of the second modification can also output incoherent light in the stacking direction.

The modified refractive index region 22 may be arranged as in the third modification shown in FIGS. 11 and 12 or the fourth modification shown in FIGS. 13 and 14. In the third modification and the fourth modification, the position of the center of gravity G of each of the plurality of modified refractive index regions 22 with respect to the lattice point O is set according to a predetermined modulation pattern. In other words, the position of the center of gravity G of each of the plurality of modified refractive index regions 22 is shifted from the lattice point O according to a predetermined modulation pattern. Thereby, the spatial phase of output light can be modulated according to the modulation pattern, and light having a shape according to the modulation pattern can be output in the stacking direction. That is, in the third modification and the fourth modification, the optical diffraction layer 13 also functions as a phase modulation layer.

As shown in FIGS. 11 and 12, in the third modification, the position of the center of gravity G of the modified refractive index region 22 is shifted from the lattice point O in a rotational manner. Square unit constituent regions R centered on a lattice point O of a square lattice are arranged in multiple columns along the X direction and multiple rows along the Y direction, and are set in a two-dimensional manner. One plurality of modified refractive index regions 22 is provided in each unit constituent region R. Within each unit constituent region R, the center of gravity G of the modified refractive index region 22 is located away from the lattice point O. As the rotation method, for example, those described in the following references can be used.
(Reference): International Publication No. 2018-230612

In FIG. 11, the broken lines indicated by x1 to x4 indicate the center position of the unit constituent region R in the X direction, and the broken lines indicated by y1 to y3 indicate the center position of the unit constituent region R in the Y direction. Each intersection of broken lines x1 to x4 and broken lines y1 to y3 points to lattice points O(0,0) to O(3,2), which are the centers of unit constituent regions R(0,0) to R(3,2). show. The lattice constant of this virtual square lattice is a. The lattice constant a is adjusted depending on the emission wavelength.

The arrangement of the modified refractive index regions 22 is determined according to a predetermined modulation pattern. The modulation pattern is, for example, a phase distribution obtained by Fourier transforming a target shape (target image) of output light. The direction and distance by which the center of gravity G of each modified refractive index region 22 is shifted from the lattice point O is determined according to the modulation pattern. The distance r to be shifted from the lattice point O (see FIG. 12) is preferably in the range of 0<r≦0.3a, where a is the lattice constant of the square lattice. The distance r may be the same for all modified refractive index regions 22, but the distance r for some modified refractive index regions 22 may be different from the distance r for other modified refractive index regions 22. .

FIG. 12 shows an example of the arrangement of the modified refractive index regions 22 determined by the rotation method. The unit constituent region R(x,y) is defined by the s-axis and the t-axis that are orthogonal to each other at the grid point O(x,y). The s-axis is an axis parallel to the X direction, and corresponds to the broken lines x1 to x4 in FIG. The t-axis is an axis parallel to the Y direction, and corresponds to the broken lines y1 to y3 in FIG. In the st plane, the angle formed by the s-axis and a straight line passing through the grid point O(x, y) and the center of gravity G is given by φ(x, y). When the rotation angle φ(x,y) is 0°, the direction of the vector from the grid point O(x,y) toward the center of gravity G coincides with the positive direction of the s-axis. The length of the vector from the grid point O(x, y) to the center of gravity G (corresponding to the distance r) is given by r(x, y).

As shown in FIG. 11, in the optical diffraction layer 13, the rotation angle φ(x,y) of the center of gravity G of the modified refractive index region 22 around the lattice point O(x,y) is adjusted to the target shape of the output light. Accordingly, it is set independently for each unit configuration region R. The rotation angle φ(x,y) has a specific value in the unit configuration region R(x,y), but is not necessarily expressed by a specific function. For example, the rotation angle φ(x, y) is calculated from the phase term of the complex amplitude obtained by converting the target shape of the output light onto a wave number space and performing a two-dimensional inverse discrete Fourier transform on a certain wave number range of this wave number space. It is determined.

As shown in FIGS. 13 and 14, in the fourth modification, the position of the center of gravity G of the modified refractive index region 22 is shifted from the lattice point O by an axis shift method. As the shaft shift method, for example, those described in the above-mentioned references can be used.

As shown in FIG. 14, the center of gravity G of each modified refractive index region 22 is arranged on a straight line L. As shown in FIG. The straight line L is a straight line that passes through the lattice point O(x,y) of the unit constituent region R(x,y) and is inclined with respect to each side of the square lattice. The angle of inclination of the straight line L with respect to the s-axis is θ. The tilt angle θ is constant within the optical diffraction layer 13. The inclination angle θ satisfies 0°<θ<90°, and in one example, θ=45°. Alternatively, the inclination angle θ may satisfy 180°<θ<270°, and in one example, θ=225°. Alternatively, the inclination angle θ may satisfy 90°<θ<180°, and in one example, θ=135°. Alternatively, the inclination angle θ may satisfy 270°<θ<360°, and in one example, θ=315°. Thus, the inclination angle θ is an angle other than 0°, 90°, 180°, and 270°.

As shown in FIG. 13, the distance r(x,y) between the center of gravity G of each modified refractive index region 22 and the lattice point O(x,y) of the unit constituent region R(x,y) is It is set for each modified refractive index region 22 according to the target shape of output light. The distribution of distance r(x, y) has a specific value for each position determined by the values of x (x1 to x4 in the example in FIG. 13) and y (y1 to y3 in the example in FIG. 13), but it does not necessarily have a specific value. It is not necessarily expressed as a function of The distribution of the distance r(x, y) is determined from the phase distribution extracted from the complex amplitude distribution obtained by inverse Fourier transform of the target shape of the output light.

For example, as shown in FIG. 14, when the phase P (x, y) in the unit configuration region R (x, y) is P ₀ , the distance r (x, y) is set to 0, and the phase P When (x, y) is π+P ₀ , the distance r(x, y) is set to the maximum value R ₀ , and when the phase P(x, y) is −π+P ₀ , the distance r(x, y) is set to the maximum value R 0. y) is set to the minimum value −R ₀ . For the intermediate phase P(x, y), the distance r(x, y) is set so that r(x, y) = {P(x, y) - P ₀ }×R ₀ /π. Set. The initial phase P ₀ is arbitrarily set.

Also in the third modification and the fourth modification, incoherent light can be output in the stacking direction similarly to the above embodiment. Further, the position of the center of gravity G of each of the plurality of modified refractive index regions 22 with respect to the lattice point O is set according to a predetermined modulation pattern. Thereby, light having a shape corresponding to the modulation pattern can be outputted in the stacking direction. Note that, as in the third modification and the fourth modification, a configuration in which the position of the center of gravity G of each of the plurality of modified refractive index regions 22 with respect to the lattice point O is set according to a predetermined modulation pattern may also be modified. The refractive index regions 22 are included in the configuration in which the refractive index regions 22 are periodically arranged in the base layer 21 along a plane (XY plane) perpendicular to the thickness direction of the base layer 21 .

The fifth modification shown in FIG. 15(a), the sixth modification shown in FIG. 15(b), the seventh modification shown in FIG. 15(c), and the eighth modification shown in FIG. 16(a). For example, the ninth modification shown in FIG. 16(b), the tenth modification shown in FIG. 17(a), the eleventh modification shown in FIG. 17(b), and the ninth modification shown in FIG. 17(c). The first electrode 4 and the second electrode 5 may be arranged as in the twelfth modification example, the thirteenth modification example shown in FIG. 18(a), or the fourteenth modification example shown in FIG. 18(b). In FIGS. 15(a) to 18(b), the first electrode 4 is hatched for ease of understanding. Further, although the first electrode 4 and the second electrode 5 are shown adjacent to each other, there is actually a gap between the first electrode 4 and the second electrode 5, and there is a gap below the gap. A separation region 18 is provided.

As shown in FIG. 15(a), in the fifth modification, the first electrode 4 extends in a spiral shape when viewed from the Z direction. The second electrode 5 is arranged so as to be located on both sides of a part of the first electrode 4 in an arbitrary direction perpendicular to the Z direction. That is, the second electrode 5 is located on both sides of a part of the first electrode 4 in each of the first direction perpendicular to the Z direction and the second direction perpendicular to both the Z direction and the first direction. are doing.

As shown in FIG. 15(b), in the sixth modification, the first electrode 4 includes a plurality of first linear portions 4a and a first electrode that connects the ends of the first linear portions 4a. It has a connecting part 4b. The second electrodes 5 are located on both sides of each first linear portion 4a in the Y direction. Further, the second electrodes 5 are located on both sides of the first connecting portion 4b in the X direction.

As shown in FIG. 15(c), in the seventh modification, the first electrode 4 includes a plurality of first linear portions 4a and a plurality of first connection portions 4b. The plurality of first linear portions 4a are lined up along the Y direction. The plurality of first connecting portions 4b extend linearly along the Y direction, and alternately connect the ends of the first linear portions 4a adjacent to each other in the Y direction. The second electrodes 5 are located on both sides of each first linear portion 4a in the Y direction. Further, the second electrodes 5 are located on both sides of each first connection portion 4b in the X direction.

As shown in FIG. 16(a), in the eighth modification, the second electrode 5 includes two annular portions 5c, a linear portion 5d connected to the two annular portions 5c, and an outer portion 5e. have. Each annular portion 5c is formed in an annular shape, and one annular portion 5c surrounds the other annular portion 5c. The outer portion 5e is connected to the linear portion 5d and surrounds the two annular portions 5c and the linear portion 5d. The first electrode 4 is arranged within a region surrounded by the second electrode 5. The second electrode 5 is located on both sides of the first electrode 4 in any direction perpendicular to the Z direction.

As shown in FIG. 16(b), in the ninth modification, the second electrode 5 includes two annular portions 5c, two linear portions 5d connected to the two annular portions 5c, and an outer portion. 5e. Each annular portion 5c is formed in an annular shape, and one annular portion 5c surrounds the other annular portion 5c. The outer portion 5e is connected to each linear portion 5d and surrounds the two annular portions 5c and the two linear portions 5d. The first electrode 4 is arranged within a region surrounded by the second electrode 5. The second electrode 5 is located on both sides of the first electrode 4 in any direction perpendicular to the Z direction.

As shown in FIG. 17(a), in the tenth modification, the second electrode 5 extends in a hexagonal lattice shape. The first electrode 4 is arranged within a region surrounded by the second electrode 5. The second electrode 5 is located on both sides of the first electrode 4 in any direction perpendicular to the Z direction.

As shown in FIG. 17(b), in the eleventh modification, the second electrode 5 includes a plurality of second linear portions 5a and an outer portion 5e. The outer portion 5e is formed into a rectangular ring shape. Each second linear portion 5a extends obliquely with respect to the X direction and the Y direction. The plurality of second linear portions 5a include two second linear portions 5a each extending along the diagonal of the outer portion 5e, and four linear portions extending so as to connect the midpoints of each side of the outer portion 5e. and two second linear portions 5a. The first electrode 4 is arranged within a region surrounded by the second electrode 5. The second electrode 5 is located on both sides of the first electrode 4 in any direction perpendicular to the Z direction.

In the twelfth modification shown in FIG. 17(c), the second electrode 5 includes a plurality of second linear portions 5a and an outer portion 5e. The outer portion 5e is formed into a rectangular ring shape. Each second linear portion 5a extends obliquely with respect to the X direction and the Y direction. The plurality of second linear portions 5a are arranged at equal intervals along a direction inclined with respect to the X direction and the Y direction. The first electrode 4 is arranged within a region surrounded by the second electrode 5. The second electrode 5 is located on both sides of the first electrode 4 in any direction perpendicular to the Z direction.

As shown in FIG. 18(a), in the thirteenth modification, the second electrode 5 includes a plurality of second linear parts 5a, an outer part 5e, and an inner part 5f. The inner portion 5f is formed in an annular shape. The outer part 5e is formed in an annular shape and surrounds the inner part 5f. The plurality of second linear parts 5a extend radially around the centers of the inner part 5f and the outer part 5e, and connect the inner part 5f and the outer part 5e. The plurality of second linear parts 5a are arranged at equal intervals along the circumferential direction of a circle centered on the centers of the inner part 5f and the outer part 5e. The first electrode 4 is arranged within a region surrounded by the second electrode 5. The second electrode 5 is located on both sides of the first electrode 4 in any direction perpendicular to the Z direction.

As shown in FIG. 18(b), in the fourteenth modification, the second electrode 5 includes a plurality of second linear portions 5a and an outer portion 5e. The outer portion 5e is formed into a rectangular ring shape. Each second linear portion 5a extends along the X direction. The plurality of second linear portions 5a are lined up along the Y direction. The interval between adjacent second linear portions 5a is not constant, but differs for each adjacent second linear portion 5a. The first electrode 4 is arranged within a region surrounded by the second electrode 5. The second electrode 5 is located on both sides of the first electrode 4 in any direction perpendicular to the Z direction.

Also in the sixth to fourteenth modifications, incoherent light can be output in the stacking direction, similarly to the above embodiment.

The present invention is not limited to the embodiments and modifications described above. For example, the materials and shapes of each structure are not limited to the materials and shapes described above, and various materials and shapes can be employed. In the embodiments and modifications described above, the end of the separation region 18 is located within the upper cladding layer 14, but the separation region 18 may extend from the upper cladding layer 14 to the light diffraction layer 13. In this case, electrical isolation between the first region 101 and the second region 102 can be further ensured.

The isolation region 18 may be constituted by an impurity diffusion region in which a deep level is formed by impurity doping. The impurity diffusion region is formed by doping the stacked body 10 with iron, oxygen, chromium, etc., for example, by thermal diffusion or ion implantation. Alternatively, the isolation region 18 may be constituted by a semiconductor region having a different conductivity type from the upper cladding layer 14. For example, if the upper cladding layer 14 is a p-type semiconductor, the isolation region 18 may be formed by an n-type or i-type semiconductor region. Alternatively, the isolation region 18 may be constituted by a semiconductor region having a different impurity concentration from the upper cladding layer 14. For example, the isolation region 18 may be formed of a semiconductor region that has a lower impurity concentration than the upper cladding layer 14 and has the same conductivity type as the upper cladding layer 14. Even if the isolation region 18 is constituted by an impurity diffusion region, a semiconductor region with a conductivity type different from that of the upper cladding layer 14, or a semiconductor region with a different impurity concentration from the upper cladding layer 14, light reflection in the isolation region 18 is prevented. can be suppressed, and resonance of light generated in the first region 101 can be effectively suppressed. Separation region 18 may be constituted by a void.

In the above embodiments and modifications, one counter electrode 6 was provided on the back surface 2b of the semiconductor substrate 2 as a common electrode, but a plurality of counter electrodes 6 may be provided on the back surface 2b of the semiconductor substrate 2. . The plurality of modified refractive index regions 22 may be provided only in a portion that overlaps with the first region 101 when viewed from the Z direction. In this case, the plurality of modified refractive index regions 22 may be provided in at least a portion of the portion overlapping with the first region 101 when viewed from the Z direction. In the above embodiments and modifications, the lattice points O constitute a square lattice, but the lattice points O may constitute a triangular lattice or a hexagonal lattice.

In the embodiment described above, AC voltages having opposite phases may be applied to the first electrode 4 and the second electrode 5. In this case, the first region 101 and the second region 102 alternately function as a gain region and a loss region. That is, while one of the first region 101 and the second region 102 functions as a gain region, the other functions as a loss region. In the first modification shown in FIGS. 5 to 7, the first electrode 4 is configured as a transparent electrode, and the opening 6a may not be provided in the counter electrode 6. In this case, the light from the optical diffraction layer 13 passes through the upper cladding layer 14 and the contact layer 15, is transmitted through the first electrode 4, and is output in the Z direction. Alternatively, in the first modification, the opening 6a is not provided in the counter electrode 6, the counter electrode 6 is formed as a transparent electrode, and the light passes through the counter electrode 6 and is output from the back surface 2b side of the semiconductor substrate 2. good. The second electrode 5 does not necessarily have to be located on both sides of at least a part of the first electrode 4 in the direction perpendicular to the Z direction, but on one side of at least a part of the first electrode 4 in the direction perpendicular to the Z direction. It may be located only on the side. That is, the second electrode 5 may be arranged on one side of the first electrode 4. Even in this case, incoherent light can be output in the stacking direction.

1A, 1B, 1C...Semiconductor light emitting element, 2...Semiconductor substrate, 4...First electrode, 4a...First linear portion, 5...Second electrode, 6...Counter electrode, 10...Laminated body, 11...Lower cladding layer (first cladding layer), 12... active layer, 13... light diffraction layer, 14... upper cladding layer (second cladding layer), 18... separation region, 21... basic layer, 22... modified refractive index region, 101... First region, 102... Second region, G... Center of gravity of the modified refractive index region, O... Lattice point.

Claims (9)

an active layer, a first cladding layer and a second cladding layer sandwiching the active layer, and an active layer provided between the active layer and the first cladding layer, or between the active layer and the second cladding layer. a laminate having a light diffraction layer;
a first electrode and a second electrode provided on the second cladding layer so as to be spaced apart from each other;
at least one counter electrode provided on the opposite side of the first electrode and the second electrode with respect to the laminate,
The light diffraction layer includes a base layer and a plurality of layers having a refractive index different from that of the base layer and arranged periodically in the base layer along a plane perpendicular to the thickness direction of the base layer. and a modified refractive index region,
The second electrode is arranged to be located on both sides of at least a portion of the first electrode in one direction perpendicular to the lamination direction of the laminate,
The laminate is provided with a separation region that electrically isolates a first region under the first electrode and a second region under the second electrode,
In the base layer, the plurality of modified refractive index regions overlap with the first region and the second region such that an array end is located in the second region when viewed from the stacking direction. A semiconductor light emitting device arranged periodically over a section . 1 . The isolation region is comprised of an ion implantation region, an impurity diffusion region, a semiconductor region having a different conductivity type from the second cladding layer, or a semiconductor region having a different impurity concentration from the second cladding layer. The semiconductor light emitting device described in . The optical diffraction layer is provided between the active layer and the second cladding layer,
3. The semiconductor light emitting device according to claim 1, wherein the separation region extends from the second cladding layer to the optical diffraction layer. further comprising a semiconductor substrate;
The laminate is arranged on the semiconductor substrate such that the first cladding layer is located on the semiconductor substrate side with respect to the second cladding layer,
4. The semiconductor light emitting device according to claim 1, wherein the optical diffraction layer is provided between the active layer and the second cladding layer. The semiconductor light emitting device according to claim 1, wherein the first electrode has a linearly extending portion. The first electrode has a plurality of first linear parts,
6. The semiconductor light emitting device according to claim 1 , wherein the second electrode has a plurality of second linear parts arranged alternately with the plurality of first linear parts. 5. The semiconductor light emitting device according to claim 1, wherein the first electrode is surrounded by the second electrode when viewed from the stacking direction. When a group of virtual lattice points is set in the base layer along a plane perpendicular to the thickness direction of the base layer, the position of the center of gravity of each of the plurality of modified refractive index regions with respect to the lattice point is 8. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is set according to a predetermined modulation pattern. The first region functions as a gain region by applying a forward bias between the first electrode and the at least one counter electrode,
The semiconductor light emitting device according to any one of claims 1 to 8 , wherein the second region functions as a loss region by applying a reverse bias between the second electrode and the at least one counter electrode. element.

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